An In-Depth Look At Axicons

An axicon is a conical prism defined by its alpha (α) and apex angles. Unlike a converging lens (e.g. a plano-convex (PCX), double-convex (DCX), or aspheric lens), which is designed to focus a light source to a single point on the optical axis, an axicon uses interference to create a focal line along the optical axis (Figure 1). Within the beam overlap region (called the depth of focus, DOF), the axicon can replicate the properties of a Bessel beam, a beam comprised of rings equal in power to one another. The Bessel beam region may be thought of as the interference of conical waves formed by the axicon.¹

Figure 1: Schematic of an axicon showing the Bessel beam region in the DOF and the ring-shaped beam that propagates after the overlap region